title: L-Threonine induces heat shock protein expression and decreases apoptosis in heat-stressed intestinal epithelial cells.
abstract: OBJECTIVE
  Osmotically acting amino acids can be cytoprotective following injury. As threonine (THR) induces osmotic cell swelling, our aim was to investigate the potential for THR to induce cellular protection in intestinal epithelial cells and evaluate possible mechanisms of protection.
  
  
  METHODS
  Cells treated with a range of THR doses were evaluated following heat stress (HS) injury. Alpha-aminoisobutyric acid (AIB), a non-metabolizable amino acid analog, was used as an osmotic control. MTS assays were used to assess cell survival. Heat shock protein (HSP) expression and cleaved caspase-3 (CC3) were evaluated via Western blot. Cell morphology and cell size were analyzed via microscopy.
  
  
  RESULTS
  Following HS, THR treatment increased cell viability in a dose dependent manner vs. non-THR treated cells (CT). The non-metabolized amino acid analogue, AIB, also increased cell survival in heat-stressed cells versus HS controls. HSP70 and HSP25 expression increased with THR and AIB treatment versus HS controls. THR also increased HSP25 in non-stressed cells. Microscopic evaluation revealed both THR and AIB preserved the structural integrity of the actin cytoskeleton in heat-stressed cells versus HS controls. THR, but not AIB, enhanced nuclear translocation of HSP25 during HS. This nuclear translocation was associated with a 60% decrease in apoptosis in heat-stressed cells with THR. No antiapoptotic effect was observed with AIB.
  
  
  CONCLUSIONS
  This is the first demonstration that THR increases HSP70 and HSP 25 and protects cells from HS. THR's mechanism of protection may involve cytoskeletal stabilization, HSP up-regulation and nuclear translocation, and decreased apoptosis. THR's protection appears to involve both cell-swelling-dependent and -independent processes.
authors.affiliation: Department of Anesthesiology, University of Colorado Health Sciences Center, Aurora, Colorado, USA.
authors.forename: Christine H
authors.initials: CH
authors.lastname: Baird
authors.forename: Stefanie
authors.initials: S
authors.lastname: Niederlechner
authors.forename: Ryan
authors.initials: R
authors.lastname: Beck
authors.forename: Alyssa R
authors.initials: AR
authors.lastname: Kallweit
authors.forename: Paul E
authors.initials: PE
authors.lastname: Wischmeyer
mesh_terms: D000621:Aminoisobutyric Acids / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation; D055551:HSP27 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D051381:Rats; D013912:Threonine / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: D000621:Aminoisobutyric Acids; D055551:HSP27 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C486114:Hspb1 protein, rat; C100049:2-aminoisobutyric acid; D013912:Threonine; C505410:Casp3 protein, rat; D053148:Caspase 3
keywords: Alpha-aminoisobutyric acid; Cell survival; Cell swelling; Heat shock protein 25; Heat shock protein 70; IEC-18